Lubricating oil composition



Patented May 25, 1943 v LUBRICATING OIL CODIPOSXTION Vance N. Jenkins, Palos Verdes Estates, CaliL, as-

signor to Union Oil Company of C aliiomia, Los.

, Angeles Calif., a corporation of California No Drawing. Application November 21, 1939, Serial No. 305,494

16 Claims.

This invention relates tomineral lubricating oils for automotive use which have been modified by the addition of constituents to impart special characteristics especially where they are adapted to severe service uses such as are encountered in Diesel engines, high output aviation engines and .the like.

deposition of lacquer-like and carbonaceous ma terials in the engine. Previously in an effort to overcome'these diii'iculties various types of metal soaps of fatty acids and the like have been introducedinto the lubricating oil, and they have exhibited a detergent effect in that they have acted to prevent 'such depositions. However, in

general, it has been observed that in those engines fitted with certain types of bearings, suchas cadmium-silver or copper-lead bearings, the use of such fatty acid soap-compounded oils has given rise to bearing corrosion, such corrosion apparently being due to the formationin the oil of corrosive materials of acidic character. The

' formation of these corrosive materials may even be catalyzed by the presence of such soaps in the oil. Some metal soaps added as detergents have required the use of free fatty acid and thelike to'act as a common solvent to promote solution of the soaps in the 011, and the presence of such free acidity has also probably contributed to the corrosion of alloy bearings of the type mentioned above.

Primarily the object of this invention is to produce for such severe service conditions as are encountered in Diesel engines, lubricating oils which will avoid the deposition of lacquer and varnish-like materials upon pistons, and overcome carbon deposition behind the rings and which will also benoncorrosive to corrosionsensitive bearings of the copper-lead and cadmi-' um-silver type.

The present invention resides in lubricating oils containing small amounts of oil-soluble metal salts or soaps capable of reacting with corrosive materials formed in engines during use to form metal salts of such corrosion products and liberate free acids, one or more molecules of which are capable-of condensing to form noncorrosive products; particularly these are soaps of lactoneforming acids here disclosed such as hydroxyand amino-carboxylic acids. The invention further resides in the use of the aforementioned metal salts either alone or in conjunction with oil-soluble metal salts or soaps of other organic acids, such as those of the higher molecular weight fatty acids, capable of enhancing the detergency of the oil. In addition, materials such as methyl dichloro stearate or chlorinated paraflin wax, capable of enhancing the film strength of the oil, may be incorporated along with the aforementioned metal salts.

Specifically, the present invention comprises the addition to lubricating oils of the oil-soluble metal salts of the lactoneand lactide-forming hydroxy carboxylic acids and the lactam-, lactimand lactimide-forming amino-carboxylic acids,

and for the sake of simplicity in the following specification and the claims these compounds will be referred to merely as the metal salts or metal soaps of lactone-forming acids. By the terms lactoneand-lactide-forming hydroxy and lactimideand lactamand lactim-forming amino carboxylic acids it is meant to include not only the corresponding acyclic compounds such as may be exemplified by gamma and delta hydroxy stearic acids, but also the cyclic compounds, including both carbocyclic and heterocyclic compounds, containing bothv a carboxyl group and. a hydroxyl or amino group, either one or both of which may be attached directly to the ring or to a side chain or chains attached to the ring, the carboxyl and amino or hydroxyl groups being so placed in the molecule as to permit of the characteristic iactone, lactide, lactam or lactim grouping by the elimination of one or two molecules of water as the case may be. An example of such a cyclic compound is orig-011F011 been substituted are likewise included within the scope of this invention.

Although it is not definitely known why the metal salts of the lactone-forming acids act as corrosion inhibitors and I do not wish to be bound by the theory, it is presumed that this inhibiting power is directly connected with the ability of these free acids to form lactones, iactides, lactims or lactams as the case may be. It is possible that l the metal salts of these acids react with the corrosive acids formed in the oil during use to form the metal salts of the corrosive acids, liberating the free hydroxy or amino carboxylic acids from their salts and the liberated acids in turn become converted under engine conditions into the neutral noncorrosive lactones, iactides, lactams, lac-' timsand lactimides mentioned. 7

As an indication of the manner-in which the above-mentioned compounds are presumed to react to neutralize corrosive acidity, thereby rendering the oil noncorrosive, the following exemplary equations showing the formation of a lactone may be given:

In these equations R represents a hydrocarbon radical, M represents a metal, and X represents the acid radical of a corrosive acid. In Equation 1 it will be noted that the metal salt of a gamma hydroxy carboxylic acid reacts with a corrosive acid to form a metal salt of the corrosive acid,

thereby rendering itnon orrosive, and liberates the free hydroxy carboxyl '0 acid. In Equation 2 the free hydroxy carboxyli acid, in turn, under the conditions present in t e engine, decomposes liberating water and forming a neutral noncorrosive lactone. Similar equations can be written for all the oil-soluble metal salts of lactoneforming acids.

Thus, when the salts r soaps of said "lactoneforming" acids appare tly react with carboxylic or other corrosive acids 'formed in the engine during use as above indicated, the instability of the resultant hydroxy carboxylic acids or amino carboxylic acids causes them to be transformed under the temperature conditions found in the engine to corresponding noncorrosive lactones, lactides, lactams, lactimides or lactims with the evolution of a molecule of water in the case of lactones, lactams and lactims, and of two molecules of water where two molecules interact to form the cyclic anhydrides in the case of iactides and lactimides. Some of these materials are oil-soluble, while others of these materials are'not particularly soluble, they apparently nevertheless are .peptized" or transformed into a finely. divided condition by reason of the presence of the soaps produced from the corrosive acids formed in the engine when the soapsof the lactone-forming acids react with the said formed corrosive acids.

As a result the lactones, iactides, lactams, lactimides or lactims remain in suspension and do not settle out either to cause coking or sludging conditions or to accumulate behind the piston rings or elsewhere.

Insofar as acyclic. or chain-type compounds are concerned the lactone-forming acids are those wherein the hydroxyl group appears on the alpha,

gamma, delta or certain subsequent carbons, or insimiiar positions in the case of nitrogen-bearing lactams, lactirns and lactimides. A similar relationship of the hydroxyl or amino group carries through into the cyclic or heterocyclic compounds mentioned. In the case of hydroxy acids wherethe hydroxyl appears on the beta carbon, and in the case of amino acids where theamino group appears on the beta carbon, corresponding lactones, lactides, lactams, lactims and lactimides do not form; instead, other acids form and therefore these materials are not suitable for the present.-

purpose. In addition, the salts of the very low molecular weight lactone hydroxy or amino acids, that is, in a range below about 10 carbon atoms per moleclue do not produce soaps suiliciently soluble in lubricating oils. .Therefore, in general, materials having more than about 10 carbons per molecule are required.

For convenience of reference general structures of the resultant "lactone-forming materials are 4 here given, It and R representing aliphatic groups:

Lactones (cyclic esters from gamma, deltaand Lactims (isomeric with lactams) R C CH Lactides (cyclic double esters from alpha hydroxy acids) R. H.O. =0

Lactimides (anhydrides from alpha amino acids) (also known as diketo piperazines) H 11 O==C-NCR RCNC=0 H H I In addition there are carbocyclic and hetero cyclic lactone-forming acids of the type represented by which yields R- c -o cal-in,

In general, any oil-solubie'metal salt of a lactone-forming acid may be employed for the purpose of preventing bearing corrosion, and in the cases of the salts of those acids of higher molecular weight, they will possess sumcient bustion engines, of

2,880,241 detergen'cy to prevent the deposition of varnish-' like coatings on the pistons and carbonaceous materials behind the rings. However, in the case of the oil-soluble metal salts of the lower molecular weight lactone-forming acids, although they will prevent bearing corrosion, they may not always possess sufficient detergency to prevent the deposition of lacquer and carbonaceous materials on the pistons and rings. Under these conditions, in addition to the metal salts of the lactone-forming acids (that is, acids forming lactones, lactides, lactims and lactams), it will be desirable to employ also compounds such as the metal salts of-fatty acids, oxidized petroleum acids, rosin or hydrogenated rosin acids, which exhibit a"detergent effect" and will act to prevent the deposition of varnish-like and carbonaceous materials in the engine. Under some circumstances it may even be desirable to employ such detergent agents" in conjunction with the metal salts of the higher molecular weight lactone-forming acids in order to enhance the quality of the compounded lubricating oil insofar as its ability to prevent lacquer and carbon deposition in the engine are concerned. In general, these detergent .soaps will amount to about 0.3% to about 1% or a little more of the total composition.

Although all oil-soluble metal soaps of lactoneforming acids when dissolyed in lubricating oil will tend to inhibit the corrosion of bearings. of the cadmium-silver and copper-lead type, I prefer to employ the oil-soluble Li, Na, K, Cu, Zn, Mg, Ca, Ba, Sr, Al, Ni, Co, Mn, Cr, Sn, Pb, and

Fe salts of the "lactone-forming" acids, and I particularly prefer to employ the Ca, Ba, Mg,

and Sr salts of the lactone-forming" acids be-;

cause of their greater oil solubility. Likewise, when I employ a detergent agent in addition to the metal salts of the lactone-forming" acids,

such sulfur, are sometimes very desirable. This sulfur also tends to inhibit bearing corrosion" and the formation of the acid conditioncausing it. as elsewhere herein indicated. With metal salts of adequate oil solubility, as in the case of .the calcium salts of higher molecular weight lactone-forming acids, the base oil may be a well-refined, paraflinic-type oil.

Insofar as sources of said lactone-forming" acids for the formation of salts or soaps thereof according to this invention, are concerned, these may-be obtained from any known or preferred source or made by any desired method. Thus,

suitable acidic materials which'will result in the formation of iactones, lactides, .lactams, lactims or the mentioned lactimides may be'obtained in of material also called degras which is obtained by the oxidation of fish oils on chamois may be employed preferably after separation of the lactone-forming materials from the non- I prefer to employ the oil-soluble Li, Na, K, Cu,

Zn, Mg, Ca, Ba, Si, Al, Pb, and Fe salts of the higher molecular weight fatty acids and substituted fatty acids, the oxidized petroleum nonhydroxy-carboxylic acids, naphthenic acids, and

the like, and I particularly prefer to employv the Ca, Ba, Mg, and Sr salts of these acids.

The metal salts or soaps of the lactone-forming" acids are employed in the lubricating oil in amounts from about 0.4% or 0.5% .up to about 6.0%, the optimum being apparently from about 0.8% to about 2.0%? When a .detergent agent" such as a high molecular weight fatty acid soap for example a calcium chloro stearate is employed, it is added in amounts from about 0.2%- or 0.3% up to about 1.5%, the optimum being apparently from about 0.5% to about 1.0%.

My invention, therefore, further'resides in a lubricating oil containill a small amount of an oil-soluble. metal soap sufficient to overcome corrosive conditions in severe service internal comlactone-forming acids, either alone or combined with additional constituents adapted to assist in overcoming the deposition of. lacquer and carbonaceous materials in th engine, and with or without other constituents adapted to enhance the oiiiness or film strength of the oil.

The mineral lubricating oil employed maybe a California or naphthenic type oil which ordinarily contains about 0.5% of organically-com bined sulfur, but may contain as little as 0.15% of such sulfur. Higher sulfur content oils such as Santa Maria 3/ alley (Californial-oils containing up to 4% or even 5%,

for example 2.75% of Ii lactone-forming" hydroxy acids. Also, fish oils otherwise oxidized. may be used. Again, where such "lactone-forming acidic materials may be purchased upon the market regardless of their method of production, such acidic materials may be employed. In many instances, these materials, will themselves ,be lactones, lactides, lactams, lactims or lactimides as mentioned, which ar subject to saponification.

For example, degras. as purchased on the open market may be saponifled under heat with solutions or slurries of suitable bases such as calcium hydroxide or magnesium'hydroxide by methods well known in the arts whereby 011- soluble calcium or magnesium or similar soaps of the 'lactones and lactides' found in degras will be produced. For some uses, the entire saponiflcation product after removal of water and excess base may be used, the soaps of the lactoneforming acids being ordinarily present in sufficient quantity, and the soaps of the fatty acids acting as detergent agents. Ordinarily, the other constituents after removal of excess base will not be objectionable in the oil. However, the lactones, lactides and similar lactone-formin8 acidic materials may be separated by acidifying the whole saponiflcation mass with a mineral acid sufiicient to liberate the acids, lactones and the like. -'I'his mass, preparatory to further saponiiication, may be suitably diluted, as with mineral oil or other solvent for the lact'ones and the like. It is then saponifled only with sufiicient alkali solution to saponify those stronger" acids which are not of the lactone-forming class and are water-soluble; Upon removing the resultant soap solutions, thelactones, lactides andthe like. which are largely oil-soluble andwhose soaps are oilsoluble. will be recovered in the remaining me.-

i terial which may include oil. These lactone's and lactides in the presence of any oil in which they are carried will then be saponifled with calcium for magnesium hydroxide or the like and separated tone-forming soaps desired for'addition to lubricating oil to form compounded lubricating oils which will be non-corrosive to corrosion-sensitive bearings such as cadmium-silver and copperlead bearings used in some severe service internal combustion engines. Where appropriate, the soaps may be prepared by double decomposition, as by neutralization with caustic soda solution and metathesis of the resultant sodium soaps with a salt of a metal whose soaps are desired such as a water solution of calcium or magnesium chloride or the like to yield the desired cal-' cium or magnesium or other oil-soluble soap. In any case the soaps are properly washed to free them of objectionable salts.

It may be feasible in many instances to obtain 2,320,241 to constitute the relatively pure oi1-soluble,lac-

hydrochloric acid to "crack out? the non-lactoneforming and non-I'actide-forming and'similar materials. 'I'hereupon, a suitable base suchas caustic soda will be introduced in quantities lactone-forming" hydroxy carboxylic acids from the oxidation of mineral oil fractions, such as 1 highly refined, highly paraflinic lubricating oils,

lubricating oils or various paraffln waxes such as those known as slack waxes and deoiled waxes. As has been indicated, the alpha, gamma and .delta hydroxy carboxylic acids are lactoneforming acids and various others'attached to higher carbons in the aliphatic chains are also lactone-forming acids. On the other hand, beta hydroxycarboxylic acids and some other hydroxy acids where the hydroxyl group is attached to various carbons abovethe delta carbon.

are not lactone-forming, the beta acids for example forming other acids as previously stated. For the purpose of obtaining a predominance of the suitable gamma and delta hydroxy carboxylic acids it may be preferable to oxidize slack waxes or deoiled waxes quite heavily. Again, it may be desirable to oxidize the indicated highly refined or highly solvent-treated parafilnic type lubricating oil fractions quite heavily'in order to produce as large an amount as possible of the "lactone-forming hydroxy acids. Heretoiore, in

out oxidatiombyknown methods to fairly 'high limits of oxidation. .For example, stainless steel units have been used to oxidize said lubricating oil by blowing in air under pressure at around sufficient to saponify the non-lactone-forming and non-lactide-forming and similar acids and saponification effected with heat. This will operate to leave the lactones, lactides and similar materia.ls in solution in the oil, from which solution the undesired soaps will be removed. Thereupon, the lactones, lactides and thelike will be converted into oil-soluble soaps by adding to said oil solution of lactones, lactides and the like an appropriate quantity of a suitable base such as calcium hydroxide or magnesium hydroxide, together with a suitable amount of water to produce an easily workable mass, which may then be boiled for three or four hours or for suilicient time to eiiect saponification. of the lactones, lactides-and the like whichare present and produce the required oil-soluble, lactone-forming soaps.

Excesslime or the like may be removed by filteringand the excess water removed by heating, thereby. yielding a concentrate of desired soaps in unoxidized mineral oil. If required, additional mineral oil may have been added to the batch at anytime and in suitable quantity to yield a conveniently workable mass. This oil should be of the same type in which the'soaps are finally to be blended to yield the lubricating product.

In making soaps, it may be desirable in'some cases, and especially will be true of some metals,

such as water solutions of water-soluble nitrates or chlorides of calcium or magnesium or other desired metal to form the calcium or magnesium or other desired m'etal soap of the "lactone-iorming materials, the soapsbeing washed tree of objectionable salts. Where feasible, and possible, final s'aponiflcation with certain metals may be regulated to substitute a smaller or larger proportion of the metal whereby to make the soap less or more basic as may be necessary or desirable.

more or less readily accomplished by carrying 300 F. to325 -'-F. for varying periods of time such as several hours until acid numbers in excess of about have been obtained. In order to remove from the oxidized charge the objectionable low molecular weight carboxylic acids such and similar materials present will be saponifled.

This batch, which includes unsaponifiable oil, will then be acidified with a dilute solution of a strong mineral acid such as sulfuric acid or In all instances, film strength, substitutes may be incorporated if desired, these being in the form of chlorine or other halogen, or sulfur,-or a phosphorous group, or a phenyl group, or the like entering into the molecule.' Specific mate rials which could be used are the soaps of lactones of 4 hydroxy 9 (or 10) phenyl stearic acid and 4 hydroxy monoor poly-'chlorostearic acid.

I-iaving obtained suitable soaps such as calcium or magnesium or other indicated oil-soluble metal soaps oi lactone-forming acids, either as such or in the form ofconcentrates as just described, these will then be added to any appropriate mineral lubricating oil such as a Western or California type naphthenic base heretofore mentioned, or parafllnic'type oil where the soaps are adequately soluble therein as heretofore mentioned, in amounts to providein the oil the re-' quired, proportion of soaps of lactone-fo'rming acids" to insure against development of conditions corrosive to cadmium-silver, copper-lead and other corrosion-sensitive alloy bearings. As

to obtain the soaps by double decomposition as r by neutralizing with sodium hydroxide solution and then reacting with asalt of the desired metal has been indicated, this proportion of soaps of lactone-forming acids would generally be in the order of about 0.8% to 2 or perhaps more commonly about 1.25% oi the soap.

It is tobe understood that numerous other methods for-the production of the required "lac- 1.5% of an oil-soluble detergent-type of metal tone-forming acidic materials and the soaps thereof-may be employed other than those here described, as will be understood by those skilled in the art... Therefore, these disclosures are to be taken as illustrative of certain embodiments of the generic invention and not necessararily as limitations thereon.

I claim:

1. 'A lubricating oil which is normally fluid comprising mineral lubricating oil and'between about 0.8% and 2.0% of an oil-soluble alkaline earth metal soap of organic acid of the class consisting of gamma and higher position hydroxy aliphatic acids capable of forming lactones, gamma and higher position amino aliphatic acids capable of forming lactams", amino aliphatic acids capable of forming lactims and lactimides. and cyclic hydroxy acids capable of forming lactones,

'in quantity sufficient to avoid corrosive conditions towards corrosion sensitive alloy bearings without substantial increase in the viscosity of the original lubricating oil. v

2. A normally fluid lubricating oil according to claim 1 containing a small proportion in the order of about 0.3% toabout 1% of an oil-soluble detergent soap of a saponifiable organic acid.

3; An oil according to claim 1 containing a small proportion between about 0.3% and about 1% of an oil-soluble detergent soap of a saponifiable fatty acid not substantially increasing the original viscosity of the mineral lubricating oil.

4. A lubricating oil .for severe service internal combustion engines of the Diesel engine type comprising mineral lubricating oil containing a. small proportion of an oil-soluble metal soap of a lactone-forming hydroxy acid where the position of the hydroxyl is at least as high as the gamma position.

5. An oil according to claim 4 wherein the oilv soluble soap is present in amounts between about 0.5%".and 2%.

6. .A lubricating oil accordingto claim 4 wherein a small quantity in the order or 0.3% to about gamma and higher position hydroxy aliphatic acids capable of forming lactones, gamma and higher position amino aliphatic acids capable of forming lactams, amino aliphatic acids capable of forming lactims and I'actimides, and cyclic hydroxy acids capable of forming lactones.

10. A lubricating oil according to claim 9 wherein the soap is present in the order of 0.8% to 2%.

- 11. An oil according to claim 9 wherein the organic acids from which the soap is produced contain at least about 10 carbon atoms per molecule. 12. A lubricating oil according to claim 9 wherein the organic acid portion of the soap contains at least about 10 carbon atoms per molecule and the soap is alkaline earth metal soap present between about 0.4% and about 2%.

13. A lubricating oil according to claim 9 wherein the soap contains at least about 10 carbon atoms per molecule, and the oil also contains a minor proportion of an oil-soluble detergent soap of a saponifiable organic acid.

14. An oil according to claim 1 wherein the soap is calcium soap.

15. An oil according to claim 1 containing also a minor proportion in the order of about 0.2% to about 1.5% of detergent soap of saponifiable fatty acid. v

16. An 611 according to claim 1 wherein the first mentioned soap contains at-least about 10 carbon atoms per molecule.

- VANCE N. JENKINS. 

